TY  - EJOU
AU  - Jiadong	Wang, 
AU  - 	Prabal	Kandel, Prabal	Kandel
AU  - Jian	Deng, 

TI  - Thrust	Generation	and	Flow	Structure	of	a	Flapping	Foil	in	a	Stratified	 Flow
T2  - The International Conference on Computational \& Experimental Engineering and Sciences

PY  - 2023
VL  - 27
IS  - 3
SN  - 1933-2815

AB  - The	flapping	foils	with	appropriate	locomotion	inspired	by	the	high-aspect-ratio	appendages	from	natural	
animals	 promise	 a	 new	 technical	 solution	 for	 the	propulsion	 of	 both	 aircrafts	 and	marine	 vehicles.	 The	
artificial	devices	using	such	a	novel	thrust	system	are	possibly	placed	in	a	stratified	flow	due	to	the	fact	that	
the	stratification	is	ubiquitous	throughout	real-world	environment.	Based	on	a	series	of two-dimensional	
numerical	simulations,	the	propulsive	performance	and	wake	structure	of	a	fully-activated	flapping	foil	in	a	
density	stratified	 fluid	are	investigated	in	 this	work.	 It	is	 found	 that	 the	hydrodynamic	characteristics	of	
flapping	 foils	in	 the stratified	 flow	 show	an	 obvious	 difference	with	 the	 homogeneous	 case.	The	 current	
results	 indicate	 that	 the	 stratification	 effect	 can	 enhance	 the	 propulsion	 performance	 of	 flapping	 foils	
regarding	both	the	thrust	production	and	efficiency	improvement.	Especially,	the	high	propulsive	efficiency	
exceeding	70%	is	observed	in	the	moderate-to-strong	stratification	level.	The	restoring	effect	of	buoyancy	
in	 the	 stratified	 fluid	 is	 noted	 to	 inhibit	 the	 vertical	 development	 of	 flow	 structures	 but	 promote	 their	
horizontal	growth,	leading	to	the	significantly	different	wake	patterns	in	the	stratified	flow	compared	with	
the	homogeneous	counterpart.	For	a	relatively	strong	stratification	strength,	the	wake	formation	behind	the	
flapping	foil	is	identified	to	be	a	wavelike	pattern	dominated	by	the	induced	internal	waves.	By	extending	
the	flapping	foil	propulsors	from	homogeneous	flow	to	stratified	regime,	the	present	study	is	expected	to	
contribute	 to	 the	 propulsion	 community	 in	 facilitating	 the	 fundamental	 understanding	 of	 involved	 flow	
physics	and	accelerating	the	engineering	application.
KW  - Biomimetic	propulsion;	flapping	foil;	stratified	flow;	internal	waves

DO  - 10.32604/icces.2023.09788